Hydration modifying agent for mortar or concrete with limited shrinkage

ABSTRACT

The invention concerns a hydration modifying agent for mortar and concrete comprising a combination of 30 to 80% of calcium sulphate, 3 to 60% of ethylene/propylene oxide copolymer and 0.5 to 6% of an activator for the copolymer. The invention also concerns a Portland dry cement comprising 2 to 10 wt. % of said hydration modifying agent and a method for preparing such a mortar or concrete composition, and a self-spreading concrete topping made from said mortar or concrete composition.

The present invention relates to a hydration modifier for mortar orconcrete making it possible to obtain a limited shrinkage, to aPortland-type dry cement composition, to a ready-to-use concretecomposition, to the process for preparing a mortar or concretecomposition, to the use of the mortar or concrete compositions for themanufacture of construction works and to the self-leveling screedsmanufactured from the mortar or concrete compositions.

In general, in order to compensate for the shrinkage of building works,it is common practice to use non-shrink admixtures which make itpossible to obtain an expansive process for mortars or concretes. Amongthese admixtures, mention may be made, for example, of micronizedaluminum powder, calcium carbide, quick lime, hydrogen peroxide, calciumsulfate, calcium aluminosulfate and iron powder. The swelling obtainedwith these non-shrink admixtures is of the order of 300 to 800 μm permeter after 28 days. The shrinkage of the cement/aggregate mix being ofthe same order of magnitude: 600 μm per meter for a mortar normalizedafter 28 days.

In theory, the shrinkage is therefore well compensated for, but in factit is very difficult to control this expansion as well as the momentthat it occurs.

It therefore appears important to develop a ready-to-use mortar orconcrete composition which does not have these problems of controllingthe expansion.

The applicant has surprisingly discovered, by turning toward atechnology other than that normally employed in the field, that a mortaror concrete composition which comprises a Portland-type cement incombination with a hydration modifier produces a modified microstructurethat does not lead to significant swelling during setting and limits theshrinkage during drying of the cementitious matrix of the mortar or ofthe concrete.

This is because the applicant noticed on the one hand that by combiningat least one Portland-type cement with a modifier comprising at leastthree ingredients in proportions defined below, it obtained a mortar orconcrete with limited shrinkage.

On the other hand, it noticed that the ingredients constituting thehydration modifier, in the proportions indicated, themselves have asynergistic action on the non-shrink effect of the Portland-type mortarsor concrete.

A first subject according to the invention is a hydration modifier formortar and concrete, comprising, in combination, from 30 to 80% ofcalcium sulfate, from 3 to 60% of ethylene oxide/propylene copolymer andfrom 0.5 to 6% of activator for the copolymer.

The calcium sulfate may be used in the form of gypsum or in anhydrousform, but in a preferred embodiment according to the invention it willbe used in anhydrous form.

The ethylene oxide/propylene copolymer is a copolymer capable of beingactivated by the addition of an activator or catalyst. It will bepossible to use copolymers differently substituted in terms of ethyleneand propylene, but in a preferred embodiment copolymers consisting of 60to 90% of ethylene oxide will be used.

The activator or catalyst makes it possible to activate the ethyleneoxide/propylene copolymer used and may be any type of suitableactivator. In a preferred embodiment, imidazole may be used as theactivator for the ethylene/propylene [sic] copolymer.

In an even more preferred embodiment according to the invention, thehydration modifier comprises 51% of calcium sulfate, 46% of ethyleneoxide/propylene copolymer and 3% of imidazole.

In another even more preferred embodiment according to the invention,the modifier comprises 80% of calcium sulfate, 18% of ethyleneoxide/propylene copolymer and 2% of imidazole.

A second subject according to the invention is a ready-to-mixPortland-type dry cement composition comprising from 2to 10% by weightof a hydration modifier according to the first subject of the invention.

The Portland-type cement may be chosen from pure or compound cements.

In a preferred embodiment according to the invention, the cementcomposition comprises from 4 to 6% by weight of a hydration modifier.

A third subject according to the invention is a ready-to-use mortar orconcrete composition comprising from 0.5 to 2.5% by weight of ahydration modifier, according to the first subject of the invention, incombination with a Portland-type cement.

In a preferred embodiment according to the invention, the mortar orconcrete composition comprises from 0.8 to 1.3% by weight of a hydrationmodifier.

The mortar or concrete compositions according to the invention mayinclude other admixtures, known per se in the art, of the type mentionedbelow.

For example, mention may be made of admixtures which act on the settingand hardening time, such as, especially, accelerators which shorten thetime between hydration of the binders and their setting, and retarderswhich extend the time between the hydration of the particles of a binderand the onset of its setting. As accelerators, mention may be made, forexample, of calcium or sodium chlorides, certain alkalis (soda, potash,ammonia) or their salts (potassium or sodium sulfate) . As retarders,mention may be made of carbohydrates (sugars, glucose, starch,cellulose), various acids or acid salts, or else zinc oxide or alkaliphosphates.

Mention may also be made of admixtures which act on the plasticity andthe compactness, such as plasticizers, thinning agents, called waterreducers, air entrainers and thickeners. As plasticizers, bentonite, fatlime, ground limestone, flyash and keiselguhr may, for example, beincorporated. As thinning agents, naphthalene sulfonate, lignosulfates,sulfonated melanine [sic], resin soaps or synthetic detergents may beused. As air entrainers, sulfonates, sodium abietate or alkaline soapsof fatty acids may, for example, be used. As thickeners orantisedimentation stabilizers, methylcellulose, silica fume, stabilizedcasein and biopolymers may be mentioned.

Mention may also be made of admixtures which improve the resistance toexternal agents, such as antifreezing agents, which protect the materialfrom the effects of frost until it has hardened; frost-preventingagents, which protect the hardened concretes from the effects of frost;waterproofing agents, which improve the impermeability of the concretesby reducing the possibilities of water penetrating by capillary effect;cure products, which prevent premature evaporation of the mixing waterand maintain the necessary hydration. As antifreezing agents, calciumchloride or sodium aluminate may, for example, be used. Asfrost-preventing agents, air entrainers may be used. As waterproofingagents, silicones, fluosilicates, colloids or resins may be used. Ascure products, emulsions of paraffins or waxes, oils, resins and variouspetroleum derivatives may, for example, be used.

The admixtures will be added in small proportions and must conform tothe French standard NF P 18-103.

Depending on the season and/or the distance from the worksite to theplace of manufacture, it will be possible, for example, to addsuperplasticizer-type rheology agents and antisedimentation agents tothe mortar or concrete composition according to the invention.

The mortar or concrete compositions, so as to have a self-levelingcharacter, may furthermore include one or more plasticizers, thinningagents, thickener and/or air entrainer.

This list is not exhaustive and the formulation of the mortar orconcrete composition may be completed by adhesion promoters and antifoamagents.

In a preferred embodiment according to the invention, the mortar orconcrete composition with a self-leveling character furthermore includesfrom 1 to 5% by weight of a thinning agent with respect to the weight ofcement.

The mortar thus obtained may be pumped and spreads by itself. All thatis required is to respect the levels to be attained and to carry out anoutgassing operation. The building work thus constructed, such as ascreed, presents the same ease of implementation as a self-levelingscreed of the calcium-sulfate type, but with water insensitivity and theability to bond to tiles in very short times. It is therefore possibleto cast outdoors, and resistance to moisture penetration is obtained.

A fourth subject according to the invention is a process for preparing amortar or concrete composition according to the invention, comprisingthe introduction of the hydration modifier either during the manufactureof the cement or during the mixing, after the mortar or concretecomposition has been mixed.

A fifth subject according to the invention is the use of a mortar orconcrete composition according to the invention for the manufacture ofconstruction elements in the field of buildings, roads and airports,and, for example, for the manufacture of waterproofing mortars orimpermeable concretes.

In a preferred embodiment according to the invention, a mortar orconcrete composition with a self-leveling character according to theinvention is used, for the manufacture in the field of floors [sic], andmore particularly of screeds.

Finally, a sixth subject according to the invention is a self-levelingscreed manufactured from a mortar or concrete composition with aself-leveling character.

The advantage of the screeds according to the invention, manufacturedfrom mortar or concrete compositions with a self-leveling characteraccording to the invention, is that there is no risk of secondarycrystallization of the ettringitic nature at the screed/tiling interfaceor screed/concrete substrate interface. In addition, it is notnecessary, as in the case of calcium-sulfate-based screeds, to useprimer-type layers for isolating the adhesive from the cast substrate.

FIG. 1 shows the shrinkage of a cement, depending on the composition ofthe hydration modifier in the Portland-type cement (68% of calciumsulfate, 30% of ethylene/propylene [sic] copolymer and 2% of imidazole).

The control contains no hydration modifier.

Anhydrite means anhydrous calcium sulfate.

CoPol means ethylene oxide/propylene copolymer.

Imid means imidazol.

The shrinkage results, depending on the ingredient or ingredients orconstituents added, are iven in the following table.

An + CoPol + Days Control Anhydrite CoPol + Imid Imid 0 0 0 0 0 5 −14082 −50 64 10 −190 30 −78 64 15 −250 −70 −108 24 20 −370 −214 −168 −36 25−470 −350 −230 −100 30 −600 −500 −290 −135

It is clearly apparent that the combination of calcium sulfate,ethylene/propylene [sic] copolymer and imidazole makes it possible toobtain a synergistic effect on the shrinkage of the cement.

The examples which follow are used to illustrate the invention, but inno way constitute a limitation to the scope of the appended claims. TESTMETHODOLOGY:

1—Laboratory tests:

a) mixing procedure: this is carried out in accordance with theprovisions of the EN 196-1 standard. The constituents (sand, cement,additive and water) are introduced in the following ratios:

Sand/Cement ratio=3

Modifier/Cement ratio=0.053

Water/Cement (W/C) ratio=0.50.

After the standardized cycle, the modifier is introduced, this beingfollowed by high-speed mixing for 4 minutes;

b) forming the test specimens: the mortar coming from mixing is put intothe shrinkage molds, having dimensions of 4×4×16 cm or 7×7×49 cm, themolds being equipped with shrinkage blocks according to the NF P 15-433standard. In the case of self-leveling mortars, they are formed as asingle course, without vibration;

c) storage conditions:

After mixing, the molds are stored in a wet atmosphere at 95% relativehumidity and 20° C. After 24 h, the test specimens are then stored inthe laboratory atmosphere at 20° C. and 50% relative humidity until 48hours have elapsed;

d) measurement conditions

For reasons of comparison with the worksite controls, the measurementsof which start after 48 h, the initial measurement of the laboratorytests takes place under the same conditions.

2—Worksite tests:

a) Production of the test specimens: the mortar coming from mixing inthe concrete mixer is put into the shrinkage molds, having dimensions of7×7×49 cm or 7×7×28 cm, these being equipped with shrinkage blocks. Theself-leveling mortars are laid as a single course, without vibration.The test specimens are stored on the worksite until 24 h of hardening,with a device preventing premature evaporation during setting. After 24h, the test specimens are moved to the measurement laboratory.

b) Measurement conditions: the initial measurement is carried out after48 h.

The performance characteristics relating to the invention may beattained by, inter alia, the following implementary examples.

EXAMPLE 1

Mixing, in a concrete mixer, of a mortar of the following composition:

Cement 450[lacuna] of CEMII B 32.5 R

0/5 Sand 1400 kg of silico-calcareous sand

Water 200 l (W/C ratio=0.44)

with or without hydration modifier according to the invention.

The modifier is introduced at the end of the mixing sequence, beforedischarge from the mixer truck. On arriving at the worksite, the mixertruck, in order to avoid any tendency toward segregation, mayadvantageously carry out a rapid-rotation sequence lasting one minuteper cubic meter after optionally having added a thinning agent.

The non-shrink performance is assessed by measuring the dimensionalvariations of the test specimens that were produced, according to thearrangements mentioned in the paragraph relating to the testmethodology, and manufactured with:

on the one hand, the above formulation without modifier: 28-dayshrinkage>500 μm/m

on the other hand, the same formulation with 18 kg of modifier accordingto the invention (containing 51% of anhydrous calcium sulfate, 46% ofethylene oxide/propylene copolymer, 3% of imidazole): 28-day shrinkage<at [sic] 150 μm/m.

EXAMPLE 2

Mixing, in a concrete mixer, of a concrete of the following composition:

cement 350 kg of CEMII A 42.5 R

0/5 Sand . . . . . . . . 800 kg

Water . . . . . . . . . . . 180 1

with or without hydration modifier according to the invention.

The modifier is introduced at the end of the mixing sequence, beforedischarge from the mixer truck. On arriving at the worksite, the mixertruck, in order to avoid any tendency toward segregation, mayadvantageously carry out a rapid-rotation sequence lasting one minuteper cubic meter after optionally having added a thinning agent.

The non-shrink performance is assessed by measuring the dimensionalvariations of the test specimens that were produced, according to thearrangements mentioned in the paragraph relating to the testmethodology, and manufactured with:

on the one hand, the above formulation without modifier: 28-dayshrinkage>350 μm/m

on the other hand, the same formulation with 20 kg of modifier accordingto the invention (containing 80% of anhydrous calcium sulfate, 18% ofethylene oxide/propylene copolymer, 2% of imidazole): 28-dayshrinkage<at [sic] 150μm/m.

EXAMPLE 3

Mixing, in a concrete mixer, of a self-leveling mortar of the followingcomposition:

cement 450 kg of CEMII B 32.5 R

0/5 Sand 1400 kg

Thinning agent

(powder) 3 kg of naphthalene-sulfonate type

Antifoam 100 g of biopolysaccharide type

Water 280 1

with or without hydration modifier according to the invention.

The modifier is introduced at the end of the mixing sequence, beforedischarge from the mixer truck. On arriving at the worksite, the mixertruck, in order to avoid any tendency toward segregation, mayadvantageously carry out a rapid-rotation sequence lasting one minuteper cubic meter.

The thinning agent is introduced upon arrival at the worksite, after thespread property of the mortar has been checked. Measured using a cone ofheight h=120 mm/base diameter: 133 mm/top diameter: 89 mm. The initialspread of the mortar is about 200 mm. After introducing the thinningagent and after the rapid-rotation sequence, this spread is then 400 mm,i.e. an equivalent of 700 mm with the Abrams cone.

Under these conditions, the shrinkage properties (on 7×7×49 cm testspecimens) of this complete formulation and of that without the modifierare as follows:

Formulation without modifier S (28 days)>500 μm

Formulation with 28 kg of modifier, as described in Example 1 S (28days)<150 μm

The compressive strength measured on 11×22 cm cylindrical test specimensis about 23 MPa after 28 days.

EXAMPLE 4

Increasing the aggregate content and incorporating polypropylene fibersalso make it possible to achieve the properties associated with theinvention, as the following example shows:

Cement 400 kg of CEMII A 42.5 R

0/5 Sand 800 kg of silico-calcareous sand

5/12 Gravel 800 kg

Thinning agent 2.7 kg of sulfonated-melamine type

Antisegregation 300 g of methylcellulose type

Antifoam 100 g of silicone type

Polypropylene fibers 1 kg

Water 190 l

with 25 kg or no hydration modifier as described in Example 2.

Under these conditions, the measured properties are as follows:

7 × 7 × 49 cm With Without Test specimens modifier modifier Initialslump with 14-16 cm 14-16 cm Abrams cone Spread after thinning 65-70 cm65-70 cm (Abrams cone) 28-day shrinkage <100 μm/m >300 μm/m (50% RH/20°C.) Compressive strength 28-33 MPa 28-33 MPa (11 × 22 cm cylinders)

What is claimed is:
 1. A method for making a construction work,comprising: preparing or obtaining a hydration modifying composition,comprising: 30-80 percent by weight of calcium sulfate; 3-60 percent byweight of ethylene oxide/propylene copolymer; and 0.5-6 percent byweight of an activator; mixing a Portland cement with the hydrationmodifying composition to obtain a cement or mortar composition; mixingwater with the cement or mortar composition or with he hydrationmodifying composition when it is mixed with the Portland type cement toobtain a slurry; and shaping the slurry in the construction work andsetting and drying the construction work, wherein swelling and shrinkageare controlled during setting and drying by the hydration modifyingcomposition.
 2. The method of claim 1, wherein the activator isimidazole.
 3. The method of claim 1, wherein at least one of: thecalcium sulfate is anhydrous; the ethylene oxide/propylene copolymercomprises from 60-90 percent by weight of ethylene oxide; and theactivator is imidazole.
 4. The method of claim 1, wherein the hydrationmodifying composition comprises: 80 percent by weight of calciumsulfate; 18 percent by weight of ethylene oxide/propylene copolymer; and2 percent by weight of imidazole.
 5. The method of claim 1, wherein thecement or mortar composition comprises 2-10 percent by weight of thehydration modifying composition, before water is added.
 6. The method ofclaim 5, wherein the cement or mortar composition comprises 4-6 percentby weight of the hydration modifying composition, before water is added.7. A self-leveling screed manufactured by the method of claim 1.